Basically, the answer is no, a standalone training course cannot make you competent.
Although the course may include some form of formal assessment it will likely be conducted on one day in a non-contextual environment; ie not in the real workplace
Assessment of competence must take place over a range of activities in the real workplace.
Training Course can however generate some very robust knowledge evidence to support competence.
Some training courses are referred to as ‘Competency Based Training’. This can be a little mis leading and can infer it guarantees to make the candidate competent.
In practice the course will be aimed at personnel who have a vast amount of industry experience and are attending a course that contains a level of high quality assessment. An example of this could be crane operator courses. The course is normally conducted at a venue, that offers a good contextual environment for assessment. It may include state of the art simulation which can be used for assessment of competence.
As a guide you should always try and ensure any training you attend contains some form of credible assessment, offers the best contextual environment to learn, and the providers (including trainers) have some formal accreditation as a learning provider.