What is the preferred treatment for wood to prevent insect/termite infestation? I will be installing some window frames that are untreated and are not teak. Will be able to access all surfaces before installation and will apply a quality finish after discouraging the bugs. If you know the stuff and where to get it, many thanks.

most building supplies have it i think it's called shelldrite

Yes, I would recommend Shelldrite or a similar clone product called something like chaindrite. Both work well but keep well ventilated when brushing on the wood, face masks are a must.

There is another option--an organic, totally non-toxic, water based product--which gives protection from all insects inc. termites, is fire-retardant and UV protectctive also--made in Germany but slowly becoming available in Thailand--a much safer solution--and not expensive--i.e. in the region of 300 bht per litre.

Google Bio-Tecta--the local distributor is a friend of mine and is CNX based.

If Google doesn't do it for you--P.M. me for his contact details.

Chaindrite, its available in dark, light & clear.

It gives the wood a nice colour, then I varnish over it.

Looks good & it keeps the poisonous stuff in the wood & away from you.