Can my teak hardwood floor be stained to a lighter shade than the wood's natural color?

We will be sanding down to bare wood.

The hardwood is located on the 2nd floor so when the gypsum ceiling was removed from the first floor, I was able to see the underside of the unstained wood.

The color of each individual plank seems to be of different shades of darkness from each other. Anywhere from semi dark to semi light.

On that note, anyone know of any reliable hard wood floor refinishers in the BKK area?

there are 'bleaching' stains that add white pigment (solids) to the wood in varying degrees of opacity, depending on the stain mix. It's basically white-washing. In the right proportion, it lightens the wood tone, while letting the warmth & grain of the wood to come through. YOu'll need to experiment with various percentages of solids in the mix on a few sticks of the teak to find the right look you're after as well as to confirm the wood will take the stain well.

Personally, I'd never bleach stain teak, but would put a clear finish on it and then use light colored walls, drapery, art, area rugs & furniture to offset its tone. YOur preferences may vary... post pix of your results!