Nexus 9 tablet with 4G LTE support, 8.9" screen, 32GB - Google unlocked, discounted on Amazon US site for under $400 shipped, including applicable taxes.
http://www.ibtimes.com/google-nexus-...tively-2291451 (no bloatware & good for several more years ... my WiFi only Nexus 2012 (32GB) is running MM 6.0.1 and still very nice - among its use, Android TV box/tablet on the road.
http://www.ibtimes.com/google-nexus-...tively-2291451
32GB in white is going for just $350 (on 5.0 - easily upgrading to MM 6.0.1 if desired)
Staying with iOS if he is comfortable & familiar, no learning curve - how about a preowned iPad Air 2, 64GB WiFi model going for about $400 (USD) on Swappa - preferred over eBay, IMO - models with LTE are around $500+ from recent sales trending ... It's good for iOS 9.x and beyond, should be good for several more years with its hardware.
If OP can get this in the US, then it's a matter doing a MR

to deliver the gift over to Thailand (or ship it over

with DHL or whatever preferred services. )