Pohang class corvettes LOA 290′ / 88.4 m TDISP 1,200 tons (2 active, transferred to Vietnam ca. 2016 after service in South Korean Navy)
ROKS Yeosu PCC-765 soon before being decommissioned and transferred to Vietnam as HQ-20. Credit: 대한민국 국군 Republic of Korea Armed Forces, CC BY-SA 2.0 , via Wikimedia Commons
Missile Boats:
Molniya class – Tarantul variant (Project 1241.8) LOA 190′ / 58 m TDISP 560 tons. Armament upgraded with 4 quadruple Kh-35e anti-ship missiles. (8 active, 6 locally built, service since 2014)
BPS 500 (Project 12418) HQ-381 missile corvette (2001) LOA 203′ / 61.9 m TDISP 525 tons improved Pauk class design, two kits delivered from Russia, only one finished.
BPS-500 patrol boat HQ-381 ca. 2011 Credit: Olympus Ares, CC BY-SA 3.0 , via Wikimedia Commons
Osa II class (Project 205U) missile boats LOA 127′ / 38.7 m TDISP 250 tons (8 active, service since 1979)
OSA II class HQ-359, in service with the PAVN since 1980 ca. 2007. Credit: Truongsa7 at Vietnamese Wikipedia, CC BY-SA 3.0, via Wikimedia Commons
Torpedo Boats
Turya Class (Project 206M) Torpedo Boats (Hydrofoils) LOA 130′ / 39.6 m TDISP 255 tons (5 active, 1 retired, service since 1984)
A Cuban Navy Turya Class Hydrofoil Torpedo Boat, flying on its hydroplanes, 1984. NARA: 330-CFD-DN-SN-84-10426
Although the resolution is typically bad, this more oblique view shows the hydroplanes projecting from outwards from the side level with the bridge. The large 57mm twin gun just aft of the awning is also a distinctive feature.Note the comparison of the Turya class hydrofoil torpedo boats and the similarly sized Osa II class missile boat at bottom.
Shershen Class (Project 206) Torpedo Boats LOA 114′ / 34.7 m TDISP 170 tons (4 active, many retired, service since 1973)
Shershen animation at speed. Credit: Eberhard Marx, CC BY-SA 3.0 , via Wikimedia Commons
Patrol Ships
Svetlyak Patrol Ships (Project 10412) LOA 162′ / 49.4 m TDISP 371 tons (6 active, service since 2003)
Svetlyak Patrol Boat Triglav, ca. 2010 of the Slovenian Navy, which is a similar export type to the six Vietnamese boats, which had the larger bow 76mm AK-176 turret. Credit: MORS (Marko Pišlar), CC BY 3.0, via Wikimedia Commons
TT-400TP Gunboat LOA 128′ / 39 m TDISP 450 tons (6 active, service since 2012) Length of these units is up to 50′ shorter than reported in Jane’s Fighting Ships and wikipedia, but the deck features match.
The Japan Maritime Self-Defense Force amphibious tank landing ship JS Kunisaki (LST 4003) passes a TT-400TP gunboat at the port of Da Nang, June 2014. (U.S. Navy photo 140606-N-QW372-023 by Lt. Jesus Uranga)
The Searchers 
