How we can make staff more effective working under you working remotely in the site?

Set clear goals and targets and review their achievements regularly, and give positive encouragement and constructive feedback.

the imported thing in a workshop is respect  for each other, and the main thing is salary and overtime, and yearly leave

that depends on your profiling abilities(delegate tasks) and recognize right persons whom could take in charge of the staff and respect the goals, you set either in your presence or remotely. and also depend on your schedule to keep a close eye on daily or weekly reports so you can evaluate and intervene when it needs to.