Gomphidia abbotti abbotti Williamson, 1907

A perching male, Cuc Phuong National Park

Gomphidia abbotti is a bulky gomphid I only spotted 3 times, in lowlands : an open, forest pond at Cuc Phuong National Park, an open stream at Huu Liên Nature Reserve and the sluggish part of a stream surrounded by rice fields - but with shrubby banks - at Hoa Binh Province.
I didn't get to see any females.

 male, Huu Liên Nature Reserve

Dorsum of synthorax with two oblique, inverted teardrop-shaped yellow spots that do not extending to the collar stripe.

Sides of synthorax deep black with two oblique yellow stripes. The area between these stripes (= metepisternum) is entirely black save for a small, isolated yellow superior spot.

Anal appendages: superiors longer than segment 10, compressed, of about even width to the apex which is squarish, separated in their entire length but converging at the apices; the inferior much shorter, a little sinuous and directed up as seen in profile.

S10 with a median dorsal spot.

Lateral view

Dorsal view

The almost black metepisternum and the characteristic two dorsal spots on the synthorax help to separate this species from other Gomphidia.

G. abbotti is known to occur in China (Guangxi, Hainan), Indonesia, Laos, Peninsular Malaysia, Myanmar, Thailand and Vietnam. 
It was recorded for the first time in Vietnam in 2010. Falls probably under the category of "not rare, just rarely seen"...