Not enough information here. We need soil type, container size, temps, lighting, fertilizers, watering regime, etc....
Oh, and pictures are always a big time plus.

Provide that kind of information and you will get more suggestions and opinions than you know what to do with.
Bruce

There are different kinds of Thai chili. Maybe what you've got is an ornamental variety which does not grow fast and big. Also, pepper need real warm weather to start growing. I have planted most of mine more than 6 weeks ago and they are hardly growing.

Do you see any buds on your plant ?

Ok here are some pictures, they have buds and two have bloomed already.
I water every other day depending on the heat and I also check soil. It's in a miracle grow soil, not sure what size the pot is but it's big enough for it to thrive. All my plants are looking so sad looking this year. I had to put those rocks in there because of my neighbors cat, they kept trying to make a litter box out of them no matter how high the pot was.

Couple more pics...

OK, just a start, but still more info is needed. Climate (where are you located). Sunlight, temps, etc.....
But, unless it is very hot and dry where you are, watering every other day is likely a problem with MG potting soil. It retains water quite well. Peppers don't like to be too wet, too long. That would be my guess with what you have stated so far.
Bruce

The rock mulch is making the soil hold even more moisture. Chances are that the plant is still the same size because root development has been non-existent. Let the dirt dry out until the plant starts to look wilty (could take a while) then give it a little water. Bet it starts to get tall soon thereafter.

Where are you?

Dennis

I live in New York City, zone seven. The weather over here has been off. Usually by this time it's nice and hot and plants are blooming. Today it's raining. My plants are getting about six hours of sunlight. They usually thrive in that area where I have always placed them throughout the years. The other side of the garden is is facing south. But I have so much weed going on over there I'm scared to put the pots on that side. I'm waiting for it to get cleaned within the next couple of days and then I will be moving the pots to that side. I've also been badly aphids on my other, pepper plants, but this pepper plant does not have any aphids. I check for aphids every day . I will not give any water to these plants for the next couple days and just see what's going on.

Cool weather will slow growth down considerably. Six hours of sun should be fine, though.

Good luck,
Dennis