The Provincial Administrative Organisation (PAO) elections will be held before other local polls, preferably before the end of the year, Prime Minister Prayut Chan-o-cha said on Tuesday.
It was the first time the PM has spelled out which of the local polls will be given priority.
The local elections are diverse, ranging from the PAO and tambon administrative organisation (TAO) polls to elections of the members of their councils.
Gen Prayut said the Election Commission and Interior Ministry would work together — the EC would take charge of arranging them and the ministry would foot the bill.
He said he was happy to clear up any confusion over the timing of the polls caused by a miscommunication between the agencies involved.
Last week, the EC rebuked the Interior Ministry for claiming it was not ready to hold local elections.
The ministry said it had to first wait for the EC to finish training its officials, but the EC insisted that could be wrapped up within a week. It said the Interior Ministry's claim that it was not ready for the polls had caused it some embarrassment.
Deputy Interior Minister Niphon Bunyamanee said on Tuesday the Bangkok governor election and city council elections would be held on the same day. This would save money, including the cost of poll staff allowances and polling station equipment. He expected it to be this year. It would be made clearer in October.
Local elections outside Bangkok would not not also take place on the same day, because that might confuse voters, Mr Niphon said.