Would like to transfer/wire a smaller amount((200 k thb) to the thai bank account,is there a certain limit(thb) at which the bank will report the transfer to the thai tax office?

I transfer always 250k from WISE to BKK bank since last year. No requests so far.

I heard (not confirmed info of course) that transferring more than 1mio. might cause an issue.

Don't worry about this too much.

They don't report on specific transactions. What they do under the Revenue Code is aggregate the total in the year and then report if:

Total Transactions: Receiving 3,000 or more deposits or inward transfers in a year (regardless of the total amount).

Amount and Volume: Receiving 400 or more deposits or inward transfers in a year AND the total accumulated value reaches THB 2 million or more.