The Malaysian variety, often hailed as "the best durian in the world," used to cost an eye-watering VND1.5 million per kilogram when it was imported from that country.
But in recent years farmers in Vietnam have been growing the fruit and its prices have been falling steadily as a result.
Mai, a farmer in the Central Highlands province of Dak Lak, has 100 Musang King trees, but their yields are only a fifth of those of the Vietnamese Ri 6 variety and Thai variety Monthong.
She sold her Musang King at VND80,000 per kilogram, down 46% year-on-year, and Monthong at 19% higher.
Kieu Oanh, a farmer in Tien Giang Province in the Mekong Delta, said the cost of tending Musang King trees is high but a tree produces only 50 kg of fruit compared to 100-250 kg for Ri 6.
Many farmers in the Central Highlands and Mekong Delta are considering abandoning Musang King altogether after suffering losses of billions of dong (VND1 billion = $39,500).
In the retail market, Musang King is sold at VND150,000-180,000 per kilogram, also down by half from last year.
Thanh Huyen, a trader in HCMC, said the quality of the variety is inconsistent in Vietnam. "I sell three durian varieties, but Musang King has the lowest sales."
Another trader, Thanh, said Monthong grown in Vietnam has higher quality than Musang King and is therefore preferred by exporters.
Vu Duc Con, deputy director of the Dak Lak Department of Agriculture and Rural Development, said musang king durian trees are best to harvest in their 10th year while Vietnamese farmers sell the fruit between the fourth and seventh years.
The area under the fruit is still small and therefore it is difficult to ensure quality for exports, he said.
More research is needed into what type of land is suitable for it before the government can educate farmers in how to grow the best quality fruit.
Dang Phuc Nguyen, general secretary of the Vietnam Fruits & Vegetables Association, said Vietnamese farmers need to improve their knowledge skills to grow this variety.
In Malaysia, farmers often place nets and wait for Musang King durians to ripen and fall, but in Vietnam, farmers cut the fruit down when they want to sell them, which lowers their quality, he added.