With the soon introduction of the ETA (Electronic Travel Authorization), which serves as a form of pre-screening for visa-exempt travelers, you’ll know ahead of time if entering Thailand without a visa is viable. This removes any uncertainty at the border. For those familiar with entry procedures in Malaysia and Singapore, it works similarly: you simply scan your passport, and you’re in.
If you’re using the visa-exempt option, it’s generally advisable to spend a few days outside the country before re-entering. Being questioned at the border can be a sign that it’s time to consider applying for a visa or having a solid reason for frequent entries without one. While most of the time they will let you in, repeated entries—especially via land border crossings—could eventually lead to denial. However, you can still try another border, and in many cases you'll likely be granted entry.
Overall, traveling into Thailand has become easier due to the transition to a more civilian-led government, which has resulted in more relaxed policies. For instance, travelers can now stay up to 90 days, a recent shift reflecting this new approach. Good luck..