Sen. Herman Talmadge has received thousands of dollars in undeclared gifts in recent years from a private fund set up here years ago to handle ticket sales for Talmadge's annual birthday dinner, according to associates of the Georgia Democrat.

The birthday dinners began in 1946. In the past seven years they have yielded more than $10,000.

Talmadge acknowledged recently that he has received separated smaller donations, which were also not reported, from other friends and constituents over the years to meet his daily expenses.

The Senate Ethics Committee is investigating Talmadge's public assertion two weeks ago thathe accepted donations of up to $25 in cash from persons who gave the money to cover his out-of-pocket expenses. According to other Georgia politicians, that practice is fairly common in the state during election campaigns.

However, J. B. Valentine, counsel to the Ethics Committee, said he was not aware of the size or extent of the senator's birthday gifts. Valentine said his committee was "still marshalling the facts" and would look into the birthday gifts to Talmadge when the committee holds its next meeting Thursday.

Neither the birthday money nor the other gifts were reported by the senator on his income tax, a Talmadge spokesman said yesterday. The spokesman said both types of gifts were looked on as indivdual small presents to Talmadge and therefore not required to be reported.

No mention of the money appears in the thousands of pages of the senator's financial statements and other documents on file in the Henry County Courthouse in McDonought, Ga., where Talmadge is involved in a property dispute with his former wife, Betty.

Gordon Roberts, a spokesman for Talmadge, said yesterday that the birthday money was paid to the senator in the form of an annual check. The check was presented at the fete with "Happy Birthday" scrawled across its face, he said. Roberts said the checks averaged out to about $1,500 each with no check over $2,000.

Until last year the parties were held at Talmadge's estate Lovejoy and often drew over 400 guests, with the men paying $25 each and the women $15. After Talmadge's divorce the party was shifted last year to the Atlanta Hilton Hotel.

John Maloof, an Atlanta attorney and long-time friend of Talmadge, said in an interview here that he ran the parties and served as chairman of the Talmadge Birthday Party Committee, which handled the dinner's finances and ticket sales. Maloof said the tickets were sold only to close friends of Talmadge or "those who wanted to give the senator something to honor him on his birthday."

Maloof said this year he mailed out 450 invitations to the part, which is scheduled for late August.

The invitations read, "This affair will commence at 5 p.m. and donations will be the same as in the past, $25 per person or $40 per couple if you wish to bring your wife or lady friend."

Persons who have attended the parties in past years and those intimately acquainted with Talmadge said that most of those who attended were men and that Talmadge apparently was not acquainted with many of the guests.

Although Maloof said all proceeds from the dinners except for expenses went to Talmadge, thousands of dollars in receipts appear not to be accounted for by either the dinners' expenses or the annual check to the senator.

Last year,for example, Maloof said the Hilton charged the dinner committee "about $5,600," which he said was paid by check from the committee's account at Citizens & Southern Bank here.

Maloof said additional expenses for the dinner last year were $300 for a one-man band, travel expenses for one member of a musical group which performed without pay, and outlays for printing the invitation and stamps.

According to Maloof, more than 400 persons attended the dinner, with others purchasing tickets but not attending. Most of the guests were men, according to those who atteded. At the dinner, Maloof said, Talmadge was given a $1,000 check.

Even if the guests were evenly divided between men and women it would appear that the committee ended up - after presenting Talmadge the $1,000 check - with nearly $2,000 left over, according to Maloof's figures.

Maloof declined to permit The Washington Post to see the committee records. An official of the Atlanta Hilton also declined to say how much the committee was charged for the dinner although he said a bill was presented by the hotel.

When the dinner was held at the Talmadge estate, it was catered by an Atlanta firm, According to an official of that firm, the changes to the committee for the dinner at Lovejoy would have been $10 per person at most. The official said there was no bar set up for the party.

Maloof said the money left over after the cost of running the party was presented to Talmadge. He said that he could not recall the size of the checks given to the senator in past years.

A source close to Talmadge during the time the dinners were held at Lovejoy said some of the gift checks were substantially larger than the $1,000 gift last year. On at least one accasion, the source said, a $500 check was also given to Mrs. Talmadge.

The spokesman for Talmadge said that while some of the details of the dinner have been coordinated through the senator's office, Talmadge has never been involved in the financial affairs of the dinner committee.

The spokesman said that Talmadge did not receive any income from the birthday committee except for the single annual check presented at the dinner.

He said the birthday checks were never declared as income because Talmadge took the view that, despite the lump sum gift, the check actually represented a number of small donations. "If you break down las year's check," the spokesman said, "at $1,000 it comes to about $2.50 in birthday gifts from each person."

Senate rules prohibit accepting cash gifts of more than $100 from anyone with a direct interest in legislation. Before 1977 the Senate rules required a confidential report on any gift of money over $50 from one source in a single year.

According to Inernal Revenue Service regulations, small cash gift aren't required to be declared as income if they are not given as political contributions and then converted for personal use.

Talmadge has said he didn't report ther small cash gifts anded to him by supporters here because of these regulations. The spokesman said yesterday the birthhday rifts were simiarly considered.

At a state bar assciation meeting in Savannah last week, almadge said he was not embarrassed by having taken the small cash gifts from his supporters. He criticized the controversy over the gifts and said press reports of them were "making a mountain out of a molehille."