Hello. Is it possible to be in Thailand only on single entry visa and before it expires, extend one more month, after that go to Laos and make a new single entry visa and stay another three months. I'm asking that because if I do multiple entry visa, I need 5000 euro in my bank account. I am Croatian citizen, btw.
TLDR : Answer Summary
Yes, you can extend a single entry tourist visa for an additional 30 days in Thailand. After this extension, you can travel to Laos, apply for a new single entry tourist visa at a Thai consulate, and potentially extend that visa as well. However, be aware that some consulates may scrutinize frequent visa applications, so having proof of funds and proper documentation is advisable.