Cost Guidance?

Thinking of building a pretty plain small house roughly 15 km north of KK town. Probably 70-80 m, elevated (crawl space or headroom).

Higher than average ceilings but not overdone. A few trees about.

I have access to a lot of old lumber from an old house (not teak) that appears to be in pretty good condition. Building site is available free from family member, so land cost is not an issue. Not paddy land, so no fill is required. No fence or wall anticipated. Air con in bedroom, outdoor kitchen, 1 bathroom.

Looking for best approach to take, i.e., QBlock, standard concrete, wood floors, steel/wood roof elements, wallboard, etc ..