Vietnam is not afraid to offend Taiwan but Singapore just doesn't get it.

Vietnam has been at loggerheads with China for territorial claims but Vietnam knows which side to support for its own economic benefits.

Vietnam is not afraid to offend Taiwan for China to see.

Vietnam fined Formosa for USD$500m.
http://asia.nikkei.com/Business/AC/Formosa-Plastics-fined-500m-over-toxic-waste-in-Vietnam

Vietnam clearly spelt out its one China policy.
http://en.nhandan.com.vn/politics/item/4939802-vietnam-china-issues-joint-communique.html

"The Vietnamese side affirmed to consistently pursue the one-China policy, support the peaceful development of Cross-Strait relations and China’s great cause of unification, and resolutely oppose actions for an “independent Taiwan” in any form. Vietnam does not develop any official ties with Taiwan. The Chinese side welcomes Vietnam’s stance."

What does China give to Vietnam in return?

China involves Vietnam deeply in its grandeur one-belt-one-road initiatives and helps Vietnam to get the financing it badly needs.

Project financing and railway construction.
http://news.xinhuanet.com/english/2017-05/15/c_136286256.htm

However, China isolates SG from its one-belt-one-road initiatives because we don't spell out our one-China policy clearly and we help USA to contain China.  The devious Taiwan president even tried to use SG as a pawn against China.  Therefore, we should also use Taiwan as our leverage to get more economic benefits from China but Singapore just doesn't get it.