Army chief Prayuth Chan-ocha seized power in May, vowing to restore order and push through reforms following six months of political turmoil.
"Official visits to and from Thailand have been suspended; the EU and its member states will not sign the Partnership and Cooperation Agreement with Thailand, until a democratically elected government is in place," said the draft, drawn up for adoption by the bloc's foreign ministers next Monday.
"Other agreements will, as appropriate, be affected. EU member states have already begun to review their military cooperation with Thailand," said the document, which is still being discussed by EU officials and could change.
The Partnership and Cooperation Agreement, completed last November but yet to be ratified, would boost cooperation in tourism, employment, education, migration, transport and environment as well as allow for a closer political dialogue.
It was unclear whether ongoing negotiations on a bilateral free trade agreement would be affected.
Goods traded between the EU and Thailand totalled around 32 billion euros ($43.3 billion) in 2013, according to EU data.
The draft statement said the EU would keep its relations with the southeast Asian kingdom under review and would consider further possible measures, depending on circumstances.
"Only an early and credible roadmap for a return to constitutional rule and the holding of credible and inclusive elections will allow for the EU's continued support," it said.
The EU urged the Thai military "to restore, as a matter of urgency, the legitimate democratic process and the constitution, through credible and inclusive elections". It also demanded the release of all political detainees and an end to censorship.
Gen Prayuth said on May 30 a process of reconciliation between political factions and reforms would take about a year and a general election would only be held after that.
The EU document said this announcement fell short of a credible roadmap for a return to constitutional rule.