In a small mu baan where the houses all have structures built on the flat roof already, bar this one, would a building permit be required to build a room about 5.5m x 3.5m x 2.8 high with a a sundeck?

It would probably be the lowest building on any of the roofs as the others and mostly peaked, this would be flat.

Location is Pattaya.

Many Thais build without a permit, but you shouldn’t do it. Ask at the municipality. A building permit is not expensive.

I wouldn't worry

I'm in a Moo Baan & they just build right up to the fence with windows

I'm sure they got a Permit & notified neoghbours

So not my problem if my cigerate smoke drifts into their window

I wouldn't worry
I'm in a Moo Baan & they just build right up to the fence with windows
I'm sure they got a Permit & notified neoghbours
So not my problem if my cigerate smoke drifts into their window

As a foreigner, I would worry. You are more vulnerable than a Thai national.

A building permit is cheap and you will be save.

I generally try to follow the rules and regulation in Thailand - even often Thai nationals don’t care. I am a guest here and it is my duty and my respect to this country.

1 hour ago, juehoe said:

 

As a foreigner, I would worry. You are more vulnerable than a Thai national.

A building permit is cheap and you will be save.

I generally try to follow the rules and regulation in Thailand - even often Thai nationals don’t care. I am a guest here and it is my duty and my respect to this country.

 

Well your right your only a guest so you have nothing to worry about (except abiding by your entry conditions ), so just let them do it their way since OP most probably doesn't own the property

The cost of a permit to build is a pittance. However it is legal proof of the size of your home. If there ever was a significant fire, the permit to build establishes the size of your home for replacement under your home owner policy. The minute you start skipping things like wearing a helmet on a motorbike, neglecting to wear seat belts, skipping a grounding rod in your home, blowing off road tax or blowing off real vehicle insurance you open yourself to future pain and cost.