You’re painting things in broad strokes without looking at the nuances. Singapore unlike the others you listed is not a U.S. ”ally” or treaty linked ands is in a different situation to the others in your list. Also, all the countries in yours list heavily engaged in confidence building...
Yes parachute & mechanised unit is unique in how they go into combat and fight. They could be involved in amphib ops as long as the amphib ships are available. There is long list of amphib ops which was sucessfully executed not by a marine force. No amphib delivery assets, no amphib ops...