I'd say it is better to focus on spec rather than brand (but avoiding Asus and HP). I would consider Acer again, the one I had (Aspire 4520G) was known for graphics card problems, other than that it was a good machine. Don't want to spend more than 15k as I've been replacing them every 2-3 years on average.
Looks like the following would be viable:
CPU- i3 or AMD A8/A10
RAM- 4GB (I can upgrade to 8 with the RAM from the dead Asus)
HDD- 500GB (Don't really care as my data storage is not on the laptop)
Graphics- Would be nice to get a dedicated GPU but unlikely in this price range
Battery- Needs to be half decent, but most are these days
Wifi- This is important, the Asus had a shitty realtek wireless adaptor that was forever dropping out and had no Linux drivers
Screen- 14" is fine, I travel a lot so nothing too heavy or bulky
The Asus was an i5 with 8Gb, an expensive machine at over 20k, but still pretty slow and had issues from the start, I'm putting that down to Windoze 10 though. It ran ok on Linux Mint aside from the wifi problems.
These seem to fit the bill:
http://www.lazada.co.th/dell-v3565-w568 ... UwP&rb=261
http://www.lazada.co.th/lenovo-ideapad- ... =1&sc=EUwP
http://www.lazada.co.th/acer-nb-aspire- ... =1&sc=EUwP
The Acer has the best spec.