Stay away from busses (extremely slow). If you´re alone, motorbike taxis are a fast option. Best is probably MRT/BTS (two different light rail/subway systems). MRT Lumphini is only a 2 min walk from the venue. Taxis are ok, too, but don´t agree on any fare – you will always pay more than by the meter. Lastly, Tuktuks are fun and look fun but they are definitely a money trap!