Just leave for a week and come back. I just did my first re-entry after spending 10 days outside Thailand. Absolutely no problems, not even a word from the immigration officer. They didn't ask for any financial proof, no questions, nothing.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.