Last name น้ำหวาน (Namwan 
, Sarmwai , น้ำหวาน) , throughout the world, is quite a rare cognomen. The cognomen น้ำหวาน is habitual in Ireland, where it is quite a rare surname, Australia, where it is a rare surname, and Canada. Measured by absolute frequency, this name is the most popular in the United States, Ireland, and the United Kingdom. Much less frequently, น้ำหวาน is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Namwan | Nigeria, Thailand, Norway, Myanmar, India |
| Sarmwai | Thailand |
| Sweetnam | Ireland, Canada, United Kingdom, United States, South Africa |
Aqui, Naluewan, Namburt, Nambutre, Namgasorn, Namgyart, Nammiwan, Namniml, Namnlum, Namonwan, Namparm, Namphusa, Namsaard, Namsawnag, Namsawsng, Namsawut, Namsua, Namsuey, Namsuntiey, Namswan, Namtie, Namvarn, Namwaan, Namwahn, Namwai, Namwaing, Namwak, Namwandee, Namwann, Namwansa, Namwarn, Namwee, Namwhann, Namwomg, Narmsutto, Narmwan, Narmyee, Narmyot, Nasrinee, Natoan, Ngammuean, Ngamwanrobroo, Ngamwean, Ngarmsard, Nhompan, Nramwan, Numnin, Numsoy, Numwan, Nyampong, Permchuen, Ruangjuice, Sodlard, Sodsard, Sodsury, Syrudee, Teawaim, Tomnuad, Waenurmi, Waewnam, Waewnum, and Watersweet