Down in Thomasville, Ga., they are a little surprised to hear what has happened to Frank Neel.

The former member of the Democratic state central committee has been born again as a political independent.

The air-conditioning contractor who last rode a train in 1964 has been picked as a consumer representative on the board of directors of Amtrak.

It was Jimmy Carter who decreed Neel to be an independent and a consumer representative. He had to, if he was going to get him on the Amtrak board. It already had five Democrats - all the law allows one political party. And the same law said there had to be some consumer representatives.

Carter cared enough to see that Neel was both, because Neel had long ago showed Jimmy Carter he cared, too.

In 1966, when Carter made his first, losing bid for governor of Georgia, his Thomas County campaign chairman and fundraiser was Frank H. Neel.

In 1970, when Carter ran again and won, Carter county chairman Neel was appointed to the Georgia Democratic Committee and two otehr state boards.

In the winter and spring of 1976, Neel left his $2 million-a-year business for months and campaigned for Carter in the New Hampshire, Florida, North Carolina, Wisconsin, Pennsylvania and Ohio primaries. In the fall, he joined the Peanut Brigade in New Hampshire and Vermont.

Today, the Senate Commerce Committee is scheduled to vote on Neel's appointment to the Amtrak board - the body that sets the rates and decides the routes for the federal railroad network. It should be routine.

But Sen. Robert P. Griffin (R-Mich.) is even more skeptical than the folks in Thomasville about the remarkable transformation in Frank Neel's life.

It's not the money - only $300 plus expenses for each of Amtrak's monthly meetings - Griffin says. It's the principle of the thing.

"The administration has put you forth as a consumer representative and . . . as an independent," Griffin told Neel during a brief confirmation hearing last November. "As a Republican, I don't like this at all. I think this is circumventing the purpose and intent of the statue."

Griffin said yesterday that he would raise the same objections today and insist that Neel be recalled for further questioning.

Neel says he can't understand it. He said in his orginial statement to the committee that he had voted for Dwight D. Eisenhower and Richard M. Nixon every time they ran, and he has since had at least three Republicans from his hometown write Griffin that they believed he had supported those Republican presidents against their Democratic opponents.

As for his membership on the state Democratic committee, Neel says it lasted only one year and involved only one meeting he can remember.

Further, he said in a telephone interview, "all the Republicans in Thomasville are my very dear friends. They know if it hadn't been Jimmy Carter running, I would have been very much for Jerry Ford. I just like Jimmy Carter, and if he had gone Republican, I would have been a Republican."

As for his consumer credentials, Neel said, "I'm a conservative businessman and I think I can represent the consumer as well as anyone on that board." He said he knew the problems people faced when the air conditioning broke - a condition not unknown on Amtrak trains - and thought he could give useful advice on what to do.

While it is true, he said, that he had not ridden a train in this country since 1964 - a fact Griffin brought out in the November hearing - Neel said that in the last couple months "the conductor of the Floridian has been coming by a couple times a week, between runs, and I've been furnished an amazing amount of information by him. Joe Cannon, I believe his name is."

The White House personnel office, which is treating the nomination with the sensitivity of a top-level Central Intelligence Agency appointment, refers all inquiries about Neel to the press office. There, no one professes to know how the computer picked Neel for Amtrak.

Neel says: "I just told those folks I'd be willing to help anywhere they thought I could help. I never said anything about railroads. Actually, I thought it would be something in the post office department. But, heck, I'm a guy who went into the Navy thinking I'd go to Saipan and I ended up at the Charleston Navy Yard."