What everyone here, including the red moded accounts that are answering don’t understand is this. Whether you have a visa of any kind, tourist or non immigrant, immigration can deny you entry. Your visa does not guarantee you entry. In this case, it was very simple. The OP was denied entry because immigration did not believe he is a legitimate tourist. If you enter often like this on a tourist visa, it is advised to use an agency entering over a land border. An agency that takes you to the Thai consulate in Savanaket on a visa run would be the best. However, if you insist to fly in, there are things you can do to prove you are a legitimate tourist as follows:
1. Provide a return or onward flight if asked.
2. Prove travel funds if asked
3. Prove paid up hotel accommodation if asked.
4. Provide the name and contact details of your girlfriend if that’s why you visit often.
How does the OP support himself while he is here so often during a calendar year? That’s what immigration is concerned about people working illegally. The officer was absolutely correct because with the op’s next duration of stay, that would have brought him to staying over 180 days in Thailand during one calendar year. That then makes the OP a resident for tax purposes. Tourist don’t live 6 months per year in another country. Thailand has visas in place for this. Elite visa, LTR, you can legitimately study Thai, you can legitimately work for a foundation or a company. You can get married to a Thai. Go find yourself a reliable visa agent and sort yourself out with a more long term sustainable visa if you want to stay longer.
There is no reason to be quoting laws here or referring people to expensive law firms. We need things explained in easy ways so everyone understands.
1. Why were you refused entry in simple tens ?
2. What can you do to avoid it?
3. what other visa options are available that are more sustainable?
4. Who can help me if I can’t do it myself ?