Marshall Islands (PKMJ) is a US Landing Right airport. To land there, head to this website: http://rmipa.com/transactions/airport/ (for tech stops) Commercial flights contact civilair@ntamar.net.
Fill out, make payment, then email airportops@rmipa. com, letting them know you made payment, and you’d like your PPR number. If they don’t have issues, you’ll get a number. Otherwise, they’ll ask you to land earlier/ later, and on agreement, they’ll give you the PPR number.
They are a bit slow, so you may need to call for information.