I'd say:

1. The latest Scivation Mass Gainer


If not get:

2. MHP Up your Mass


Or lastly:
3. Universal Real Gains


But eat more regularly, and take these weight gainers between meals.

However, if you can make your own weight gain drink..
- get a blender
- get some fine powdered oats (not sure if you can find in Malaysia though - if not grind your own oats)
- get any protein powder (ON Whey, MP Combat Powder or something - wouldn't recommend Myofusion because it makes the drink really thick after blending)
- get some bananas (like two 7inch bananas)
- some yoghurt
- peanut butter
- milk
- frozen blueberries if you can

I make mine with :
3 - 4 scoop fine powdered oats
2 laddles frozen blueberries
2 bananas
1 laddle yoghurt
500ml milk
1 - 2 scoops Muscle Pharm Combat Triple Berry flavour

I make mine a berry flavoured one.