Seems like it is the same. From wikipedia:
A G-string "G-Thong" or thong is a narrow piece of cloth, leather, or plastic that covers the genitals, passes between the buttocks, and is attached to a band around the hips, worn as swimwear or underwear by both men and women. The two terms G-string and thong are often used interchangeably; however, they can refer to slightly distinct pieces of clothing: The primary difference between the two garments is that a g-string has less material between the legs and buttocks, hence a string-like appearance. Variants of the thong or G-string include the V-string or G-Thong, a thong with a triangle "v" of cloth with the G-string between the legs, and the T-string, where a single string passes around the waist and between the legs, forming a T between the buttocks.
