ST_DISTANCE
functions do not use a geometry index. You should use e.g. ST_DWITHIN
so your query would be something like
select *, cast(st_distance_sphere(city_gis.point, tmp1.pnt) as int) as distance
from tmp1
inner join city_gis on st_dwithin(city_gis.point,tmp1.pnt,60000)
Here is the documentation of this function.