If you are going around several Asian countries, I highly recommend the AIS Sim2fly 4GB/8 Days Traveller Roaming. I used them in Japan, Hong Kong and Thailand and it worked on 4G data with fantastic coverage. Another plus is, you could pick these cards up on eBay or Phone shops in Hong Kong without the need to surrender your passport, an added plus as I do worry about these telco shops taking my passport details. Quite cheap too at HKD90.