Some questions...
1. What difficulty mode are you playing on?
2. What class is the PC? What class is the module designed for?
3. Does the PC have henchman options?
4. Does the PC have equitable access to equipment as the monsters he is pitted against? In other words, if the monsters are laden with magic items, does the PC have a comparable amount (or at least a chance to obtain such).
Any Warrior at 1st level is a match for a Kobold or Goblin. If you are using encounter spawns, the triggers should spawn an appropriate amount of creatures - assuming the default settings haven't been overridden by the Builder.
I have a module I am building right now for my son and have been testing it using Daeris the 1st level Dwarf Fighter. He is armed with the basic equipment provided by the class package - studded leather armor, 3 potions of cure light wounds, a short sword, and a torch. When I tested out the hardest encounter area with him, I boosted his armor by leaving a chain shirt near the entrance to the area. The area uses 4 staggered custom single-shot spawn triggers that spawn 1-2 skeletons or zombies (or a mix thereof). Despite the triggers being somewhat spread out across the area, It is possible in the course of melee for the PC to cross the next trigger, increasing the number of opponents. At the height of the encounter Daeris was fighting 2 skeleton archers, a skeleton swordsman, and a zombie. Even against those odds Daeris survived, having half his HP remaining and one cure potion left. Of course, having designed the encounter, I had a distinct advantage over a player. However, once engaged in melee, the fight was all dependent upon the tactics I used and the luck of the dice.
I guess the point is that when designing encounters, especially for low-level characters, it is best practice, IMO, to use custom encounter triggers to spawn in exactly what you want and not leave the determination of enemies to the game engine. Someone once told me that a good NWN module is designed with the same principles as a pnp adventure. Everything is staged and the only thing that should be left to random chance is the roll of the dice. In pnp, the DM always has the option of just ignoring a randomly generated encounter that is too powerful for the PCs. In NWN, once they cross that trigger, the game engine is remorseless.