Less restrictive query return less result due to simple removing one additional constraint
The FULLTEXT index acts very funny with regard to the MySQL Query Optimizer. I have written about this before:


https://stackoverflow.com/a/6092216/491757 (May 23, 2011)
FULLTEXT index ignored in BOOLEAN MODE with &#39;number of words&#39; conditional (Oct 25, 2011)
Mysql fulltext search my.cnf optimization (Jan 26, 2012)
MySQL EXPLAIN doesn&#39;t show &#39;use index&#39; for FULLTEXT (May 07, 2012)


Try refactoring your first query so that the FULLTEXT clause and the Spatial clause are not performed in the same level of the EXPLAiN plan.

SELECT * FROM
(
    SELECT DISTINCT
        TB.ID,
        TB.Latitude,
        TB.Longitude,
        111151.29341326*SQRT(pow(-6.185-TB.Latitude,2) + 
        pow(106.773 - TB.Longitude,2)*0.98839228980165) AS Distance
    FROM
    (
        SELECT * FROM `tablebusiness`
        WHERE MATCH (FullTextSearch) AGAINST
        ('kucing*' IN BOOLEAN MODE)
    ) AS TB
    join 
    (
        SELECT ID FROM tableauxiliary
        WHERE MBRContains(GeomFromText ('MULTIPOINT
        (-6.2317830813328 106.72621691867,-6.1382169186672 106.81978308133)'),TA.Latlong)
    ) as TA
    on TA.BusinessID=TB.ID
    ORDER BY
        Distance
) AA LIMIT 0, 20;