I just came into Thailand from a side trip to Vietnam. At immigration they asked for nothing, no accommodation, no airfares out, no 20k Thb, zero. Got the 30 day Visa exempt. All those restrictions are mostly in place for those who have insufficient funds or try to live in Thailand long term without the correct visa, i. e. Back to back border runs won't last forever.
I did an extension 3 weeks ago at Jomtien Without the tm30 you will get the fine. Yes 💯 hotel should do it but if they don't then you will get the fine.
33 years of coming to Thailand here. My thoughts are is to keep your money in your home country. If you happen to be an Australian then you can get 5% interest with a UBank account with a 250k government guarantee. Why bother risking it in Thailand?
I get the tourist visa in my own country because I try to avoid contact with Thai immigration. It's just less hassle and I don't waste half a day getting the extension done.
Did it 2 weeks ago at my local immigration office,1900 baht. Was in and out within an hour. Never heard of an online one and what's the point if you still have to turn up physically?