There are many different types of insect repellent available.

They do seem to work differently for different people, and if you are particularly attractive to mosquitos, you may need to use a stronger form of repellent.

100% DEET
This is quite nasty but seems to keep everything away. It's probably not best to get this near your eyes or to put it on your fingers if you're going to pick up food with them. Tends to be in a spray bottle. It does not seem to be easily available in Thailand.

50% DEET (and less)
Less nasty, but will keep insects away pretty well. Maybe still not best to get it into your eyes or to ingest it. Also not seen to be regularly available in Thailand.

Sketelone Yellow
This has about 17% DEET in, but it seems to be a good all-rounder if you are moderately attractive to mosquitos. It's in a spray bottle which is good for applying to clothes, and you can buy it everywhere, with prices varying from 70 baht to 250 baht for a large bottle.

Sketelone Green
In a spray bottle again, but this one uses citronella rather than DEET. It's more natural and possibly a little safer, but may not keep bugs away quite so well. A good all-rounder if you want to avoid DEET.

Pink bottle at the retreat shop
This smells a little like moisturisor, but it does seem to work pretty well. A small bottle of cream was about 70 baht which lasted 4 days, but could not be used on clothes.