AT FIRST the questions involved petty cash, the large number of small donations that Sen. Herman E. Talmadge said he has routinely accepted, over the years, from friends in Georgia who want to help him meet expenses. Then there were the clothes, lodging and other presents given to him, Mr. Talmadge said, by the people. And then there were the gifts, averaging about $1,500 a year, that the millionaire Georgia Democrat received from friends and admirers at his annual birthday party. It sounded a bit much at the time. But whatever you may think of the propriety of it, accepting all those friendly expressions of esteem - which have been unreported and untaxed - may be perfectly legal. That assumes, of course, that what you are talking about are gifts.

What's now turning up as a consequence of official and press inquiries into the senator's affairs, however, is a little harder to think of in terms of simple good-heartedness. Attention now centers on apparent irregularities involving the flow of funds through Sen. Talmadge's official, campaign and personal accounts.

For instance, Mr. Talmadge had reported to the Senate that he had not spent any personal funds in his 1974 campaign. In June, however, The Washington Star pointed out that his campaign committee had reported reimbursing him. In July, Mr. Talmadge filed amended reports showing that he had spent $26,912 from his own pocket for reelection efforts and had been reimbursed from his campaign account. An aide blamed the earlier, erroneous report on "mistakes" and "oversights."

During his divorce proceedings in Georgia last year, questions were raised about the use of a special office account. In June, Sen. Talmadge hired auditors and, on the basis of their report, repaid the Senate $37,125.90 last week for official expense payments that had been improperly claimed between 1972 and last year. Mr. Talmadge attributed the faulty claims - a combination of payments for outlays that were never made, and expenses that were not really official - to "errors in judgment" by his staff.

There is the further matter of the checking account in the Riggs National Bank through which nearly $40,000 moved in 1973 and 1974. The account is in the name of the Talmadge campaign. Several documents and checks bear Sen. Talmadge's signature, apparently made by an automatic signing machine. Of the deposits, nearly $12,894.67 came from Senate expense payments improperly claimed by Daniel Minchew, Sen. Talmadge's administrative assistant until October 1974. The source of the rest of the money has not been pinned down. Nor is it yet clear where the funds went or how they were used, though investigators have found that several thousand dollars were transferred to Mr. Minchew's personal account.

Sen. Talmadge said last week that he had just learned that the account was in his name, and that he had no affixed, authorized or known about "anysignatures purporting to be mine." Mr. Minchew has said, through his attorney, that "whatever was done with Sen. Talmadge's knowledge or consent or direction and on his behalf."

Simply summing up all of this makes clear how much remains to be examined by the Senate Ethics Committee, a federal grand jury and the Internal Revenue Service - all of which are now investigating this tangled affair. Judgments about responsibility, truthfulness and the like are obviously premature; it isn't even clear, yet, precisely which laws and Senate rules may have been violated, much less by whom.

We urge the agencies involved to press on. Sen. Talmadge's own statements and corrections of various records have shown a remarkably casual attitude toward little and not-so-little gifts, and an irresponsible degree of laxity in failing to oversee his staff's use of his official accounts and autopen. That's the very least that can safely be said of this affair - as of right now.