Prime Minister Prayut Chan-o-cha said he will quit politics if the United Thai Nation (UTN) Party, of which he is a prime ministerial candidate, fails to win enough House seats to form a government in Sunday's election.

Prayut spoke during a campaign rally in Nakhon Si Thammarat.

"If we win only a small number of constituency seats, I will just return home and take a rest," Prayut went on to say.

"Previously, I had to work with several parties and many groups. Some were easy to deal with, but some were not," he said.

He went on to say that: "I've spent many years as a soldier and went through several crises. Today, I am a politician. It is different. When I spoke to soldiers, I had to be firm.

"But when I speak to people, it is different, and I think I prefer this way," Prayut said.

The UTN will hold a final campaign rally today at the Queen Sirikit National Convention Center in Bangkok.

Prayut will also lead key party figures in campaigning around the city, riding on the back of a pickup truck around key districts tomorrow, which is the last day of campaigning by political parties.

By law, parties must stop their campaigns before 6pm on Saturday.