It is better to pay for instance only $12.000 annual UBI independent of work, so that there is a stimulus to step out of bed in pursuit of any additional $ of income.
How much UBI should be paid to those in working age 16 - retirement? My rule of the thumb, 70% of what one could earn in the current least full-time paying job.
PS. Children, the sick, and the pensioners should have their needs tendered to separately from UBI.