Ok, here is what I managed to do; and it should work fine with others too.
Purchased from the same eBay seller, with 4GB single slot, English+THAI keyboard layout in 40,000 INR [~660USD]
I'm not sure why there's difficulty in upgrading the RAM to 16GB (2x8GB) in
DELL Inspiron N5420-V560114TH.
On the same day of delivery, I upgraded memory to 2 x Transcend SODIMM DDR3 Synchronous 1333 MHz (
JM1333KSH-8G). (costs 5K INR | 82USD each)
After a month, upgraded to 250GB Samsung SSD (840 EVO-Series /
MZ-7TE250BW) [8K INR / 130USD]
# If anyone interested, here is the complete dump of hardware specification,
http
/pastebin.com/QS1ycz6K
* I personally didn't like battery life. weight and display quality (so this one...