Looking back on this now, I think the name of the unique unit should have been changed. Haluwbilau seems to be the correct term to refer to a soldier in Cham language, so I’ll use this name for the unique unit instead of the earlier name “Champa pirate”, which sounded a bit weird and derogatory.
Haluwbilau would be a unit wielding a large irregularly shaped shield on one hand and a short spear on the other, as illustrated below

And inspired by the Ratha, I think this unit could also switch between two modes. The default mode for the Haluwbilau is infantry and it would benefit from infantry armor upgrades as well as blacksmith melee attack upgrades, however it can be switched to a skirmisher mode with one click. And under the skirmisher mode it would benefit from ranged or pierce attack upgrades.
Haluwbilau’s stats
Trained at: Castle
Cost: Food 30 Gold 30
Training Time: 18 seconds
HP: 45 / 50 (elite)
Melee Attack: 9 / 10 (elite)
Pierce Attack: 3 / 4 (elite)
Attack Bonuses (apply to both melee and ranged modes):
+5 vs Monk
+4 vs Civilian Units (Villagers, Trade Carts, Trade Cogs)
+3 vs Ship and Fishing Ship
+2 vs Eagle Warrior
+1 / +2 (elite) vs Archer
Rate of Fire: 3 (ranged) / 2 (melee)
Frame Delay: 19 (ranged)
Attack Delay: 0.52 (ranged)
Range: 4 (ranged)
Minimum Range: 1 (ranged)
Accuracy: (ranged) 80% / 90% (elite)
Projectile Speed: 7
Melee Armor: 1
Pierce Armor: 2
Armor Classes: Archer, Infantry, Unique Unit
Speed: 1.1
LOS: 6
Ability: Can switch between infantry (melee) and skirmisher (ranged) modes