I left for and returned to Thailand on March 24th, and I renewed my Non-O visa (1 year). In the case of Sriracha, the Immigration Office doesn't ask for TM30 again. I'm not sure for all IO but I know most IO doesn't ask for it
Thailand might be not the best option. Unless you have a specific reason, you'd better consider other countries in ASEAN such as the Philippines, Indonesia, Malaysia, etc