This is nang kwak, mostly for fortune. Many of stalls/shop owner pray to this nang kwak.

Hi Lil'Maine, the main function no matter what type of the amulet is to have the efficiency to protect the safety of the amulet owner it self. Whether it is nang kwak or somdej or pidta they do have this kind of ability.  It also depends on the monk who made it, for an example, phra pidta maha ut is a kongkrapan/klaew klaad (Invincibility /Free from all harms)  type amulet, but if the monk who made it is more specialize towards fortune then this phra pidta maha ut will have the fortune elements in it.

Normally for starter they will look for somdej, phra pidta and LP Tuad amulets. you can try one of them if you dun mind.

Who exactly ask u to rent the amulet in "Sze main fo" temple at happy garden, is he a monk? Have u got chance to visit thai temple in thailand or thai temple maybe at northern part of msia (such as kedah or PG) or maybe eastern part (kelantan). Oh ya another one thai temple i think shud be nearby the four face buddha temple,  Buddhist Thai Wat Chetawan located at  No. 24, Jalan Pantai, Off Jalan Gasing, 46000 Petaling Jaya, Malaysia. Check this out,

https://sites.google.com/site/watchetawan/amulet-counters.
Dun rush in getting amulet for oneself, looks carefully if really "hap ngan yuen" in cantonese, then only u rent. In fact u can try to if possible the amulet made by that particular temple rather then get other temple amulet from the same temple. (at least own temple made amulet can assure u the genuine). I am currently wearing Tok Raja Rian made by Chau Khun Chan (AH kong, wat uttamaram) and also Srivichai second batch from Chau Khun Bao (wat Kalai).

If u are able to go to Thailand let me know which part and i can recommend u temple to visit. LOL.