Travel Asia SIM (Silver) 6 GB Non-stop internet for 10 days; Australia, South Korea, Myanmar, Malaysia, Singapore, Japan, China, Taiwan, HK and etc

To use in China: Your phone must be able to use LTE Band 39, 40 and 41 which is not common for US phone model. If not, you will get only EDGE (iPhone 7 or later model only if you want to get 4G in China).
in Mainland China. you can use all apps by this SIM card
In Japan, Roaming partner is NTT Docomo and Softbank. Your phone must be compatible with LTE Band 1, 9, 19, 21, 28 (at least 1 Band).

The carriers they use are as below;
Cambodia => Smart Axiata;;
China => China Mobile;;
Hong Kong => Hutchison H3G;
Indonesia => Indosat;;
Japan => Docomo, Softbank ;;
Macau => Hutchison;;
Malaysia => Maxis;;
Philippines => Smart;;
Singapore => Starhub;;
South Korea => SK Telecom and KT;;
Taiwan => Chunghwa;