When designing a planting scheme for your Thai garden, it is a good idea to use plants to alter a visitors perception of space.
Lighter plant colour can be used to effectively 'lenthen' the landscape, as paler colours tend to 'move away' from the viewer… Whites, greys, beiges, light blues and greens, when at a distance, will create this lengthening effect.
More vibrant, brighter colours will compete for the eyes attention, and so can be used effectively if you're attempting to hide something, like an unnattractive view beyond.